Scientists have characterised the first potentially habitable world outside our own solar system located about 31 light-years away.
Thesuper-Earth planet — named GJ 357 d — was discovered in early 2019 owing toNASA's Transiting Exoplanet Survey Satellite (TESS), a mission designed to combthe heavens for exoplanets, according to the research published in theAstrophysical Journal Letters.
"Thisis exciting, as this is humanity's first nearby super-Earth that could harbourlife — uncovered with help from TESS, our small, mighty mission with a hugereach," said Lisa Kaltenegger, associate professor of astronomy at CornellUniversity in the US and a member of the TESS science team.
Theexoplanet is more massive than our own blue planet, and Kaltenegger said thediscovery will provide insight into Earth's heavyweight planetary cousins.
"With athick atmosphere, the planet GJ 357 d could maintain liquid water on itssurface like Earth, and we could pick out signs of life with telescopes thatwill soon be online," she said.
Astronomersfrom the Institute of Astrophysics of the Canary Islands and the University ofLa Laguna, both in Spain, announced the discovery of the GJ 357 system in thejournal Astronomy & Astrophysics.
They showedthat the distant solar system — with a diminutive M-type dwarf sun, aboutone-third the size of our own sun — harbours three planets, with one of thosein that system's habitable zone: GJ 357 d.
LastFebruary, the TESS satellite observed that the dwarf sun GJ 357 dimmed veryslightly every 3.9 days, evidence of a transiting planet moving across the star'sface.
That planetwas GJ 357 b, a so-called "hot Earth" about 22 per cent larger thanEarth, according to the NASA Goddard Space Flight Center, which guides TESS.
Follow-upobservations from the ground led to the discovery of two more exoplanetarysiblings: GJ 357 c and GJ 357 d.
Theinternational team of scientists collected Earth-based telescopic data goingback two decades — to reveal the newly found exoplanets' tiny gravitationaltugs on its host star, according to NASA.
Exoplanet GJ357 c sizzles at 127 degrees Celsius and has at least 3.4 times Earth's mass.
However, thesystem's outermost known sibling planet — GJ 357 d, a super-Earth — couldprovide Earth-like conditions and orbits the dwarf star every 55.7 days at adistance about one-fifth of Earth's distance from the sun. It is not yet knownif this planet transits its sun.
Kaltenegger,doctoral candidate Jack Madden and undergraduate student Zifan Lin simulatedlight fingerprints, climates and remotely detectable spectra for a planet thatcould range from a rocky composition to a water world.
"Webuilt the first models of what this new world could be like. Just knowing thatliquid water can exist on the surface of this planet motivates scientists tofind ways of detecting signs of life," Madden said.
"If GJ357 d were to show signs of life, it would be at the top of everyone's travellist — and we could answer a 1,000-year-old question on whether we are alonein the cosmos," Kaltenegger said.